1. Technical Field
The present invention relates to a piezoelectric vibrator, and an electronic apparatus and a vehicle each equipped with the piezoelectric vibrator.
2. Related Art
In the past, there has been known a piezoelectric vibrator characterized in that excitation electrodes are respectively formed in central parts on both principal surfaces of a piezoelectric substrate, a plurality of grooves is disposed between an end in a propagation direction of a thickness-shear vibration and the excitation electrode of the piezoelectric substrate, and the thickness of the plurality of grooves in a thickness direction of the piezoelectric substrate is set so that the closer to the excitation electrode the groove is, the shallower the groove is, and the closer to the end in the longitudinal direction of the piezoelectric substrate the groove is, the deeper the groove is (see, e.g., JP-A-2011-97623, JP-A-2003-46366).
According to the documents, in the piezoelectric vibrator, by efficiently and accurately disposing the plurality of grooves on the piezoelectric substrate, and setting the depth so that the closer to the end in the longitudinal direction of the piezoelectric substrate the groove is, the deeper the groove is, the shape of the piezoelectric substrate approaches in a pseudo manner to a bevel shape (a shape with a tilted peripheral part such as a shape with a chamfered peripheral corner), and a decent energy confinement effect is expected.
However, although in the piezoelectric vibrator, the depths of the grooves gradually ascend from the vibrating region toward the periphery, regarding parts (protruding parts between the grooves) other than the grooves, the positions of the tops (upper surfaces) thereof do not change even in the direction from the vibrating region toward the periphery, and are kept the same as the position of the principal surface of the piezoelectric substrate.
Thus, the shape of the piezoelectric vibrator described above have is similar to the bevel shape with reference to the bottoms of the grooves, but is similar to a flat-plate shape with reference to the tops (upper surfaces) of the protruding parts described above. Therefore, there is a possibility that it is hard to obtain the bevel effect (the energy confinement effect) worth the shape provided with the plurality of grooves.